The invention will be described more particularly within the context of its application to a container blow-molding apparatus in which the container is obtained by blow-molding a preform produced beforehand by injection molding. This preform has a substantially tubular body which is closed at one of its axial ends. Its other end has, right from this injection-molding operation, the final shape of the neck of the container.
Generally, the neck of the container comprises a thread and, at its base, an annular support flange which extends radially outward.
FIG. 1 of the appended drawings is a perspective view illustrating a preform feed unit situated upstream of a blow-molding apparatus. The preforms are tipped as a loose mass into a bin 1. They are taken from this bin by an elevator belt 2 which tips the preforms, at a predetermined rate, into the upper end of an alignment hopper 3.
This alignment hopper 3 generally comprises two alignment rollers which are inclined with respect to the horizontal and which are substantially parallel to one another.
The two rollers are rotated in opposite directions and are separated from one another in such a way as to leave a gap between them.
This gap is slightly greater than the size of the body of the preforms and is smaller than the size of the support flange of the preforms.
Under the effect of gravity, the preforms are forced toward the bottom of the hopper where the two rollers are situated.
The rotational movement of the rollers and their inclination with respect to the horizontal ensure that the preforms are placed behind one another, suspended by their flanges bearing against the rollers.
The preforms slide along the axis of the rollers, toward the bottom of the hopper where they are collected in a feed rail 4 itself connected to the blow-molding machine (not shown).
Since the preforms are tipped as a loose mass into the bin 1, it is possible for some preforms not to be correctly placed between the rollers of the alignment hopper 3.
Of course, the improperly oriented preforms cannot be introduced into the feed rail 4 which leads to the blow-molding machine.
The same applies to preforms which are nested inside one another, even if the lower preform in this nesting arrangement is correctly oriented.
Hence, means for ejecting improperly oriented preforms or ones nested inside one another are generally provided to prevent preforms in such a configuration from joining the feed rail.
The feed rail 4 typically comprises a rectilinear part and a curved part, the curvature generally being partly in-plane, that is to say that the curvature is situated within one and the same plane, and partly out-of-plane, that is to say that a single plane in which the curvature remains cannot be defined, thereby generally forming a helical segment which can be composed over at least some of the curvature of a segment having planar curvature.
The formation of a segment section having helical curvature with some of the curvature being out-of-plane and/or some of the curvature being in-plane makes it possible to maintain a slope down which the preforms can flow by gravity.
The in-plane and out-of-plane curvature, namely the formation of a segment section having planar curvature (situated within the same plane) and/or a segment section having curvature which is not situated within the same plane, makes it possible for the preforms to enter the blow-molding machine without the unit represented in FIG. 1 interfering with maintenance interventions and operations on the blow-molding machine, the entire apparatus nevertheless remaining compact.
It is in fact desired for all the components of the blow-molding machines to remain easily accessible, by opening doors, and removing doors and cowlings.
The fitting of curved sections in the feed rail 4 makes it possible for the unit represented in FIG. 1 to be placed optimally with respect to the blow-molding machine so as to minimize the overall space occupied by a machine for blow-molding containers.
By way of example, the alignment rollers of the hopper 3 are substantially parallel to the linear oven used to heat-treat the preforms.
In the feed rail 4, the guides on which the preforms are suspended are formed by bearing and sliding sections for the preforms.
The bent part of the feed rail 4, which part is curved in-plane and most often out-of-plane, that is to say forming a segment section having planar curvature (situated within the same plane) and/or a segment section having curvature not within the same plane, constitutes a difficult passage for the preforms. Everything must be set up so as to prevent the preforms from remaining jammed in this curve or bent portion.
To enable preforms of different sizes to be conveyed by gravity, it is desirable for the guide rail to be provided with a pair of runners whose spacing can be modified, thus allowing the spacing between the runners to be quickly adapted to the diameter of the neck of the preforms.
In order to be able to modify the spacing of the two runners of a rail for conveying suspended objects such as bottles, it has been proposed to place actuators which allow the runners to be shifted substantially perpendicularly to the direction of travel of the bottles.
Nevertheless, in the case of the curved conveying sections, the provision of actuators is a relatively complex undertaking, since modifying the opening of the conveying rail has to take place with a controlled radius of curvature, and without the length of the runners being modified toward the inside or outside of the curve.
As a result, the extent to which runners or “under-neck guides” can be adjusted in existing devices is relatively small.
Document CA 2 419 562, in the name of Sidel Canada Inc, discloses an adjustable curved pneumatic bottle-transporting device. Although operationally satisfactory, this device proves to be complex and costly to mount.
Taking account of the difficulties mentioned above, and given that a technically and economically more satisfactory solution is not available, what happens in practice at present is that the bent portions of the preform feed rails are purely and simply changed in their entirety when the spacing of the runners has to be modified.
Moreover, this is done in spite of the relatively long time required for such an operation, during which time the container-forming machine cannot operate, resulting in a reduction in the profitability of the machine.
It would therefore be particularly beneficial to provide means which make it possible to modify the spacing of the runners on curved rail sections in a minimum of time and with maintenance operations which are simple to carry out.
Furthermore, it is necessary to provide a helically curved rail section for each type, in particular for each under-flange diameter, of preforms that it is wished to transport, making subsequent storage locations necessary. It would therefore be advantageous to produce means for modifying the spacing of the runners that are not bulky and can be stored and transported easily.
Moreover, since the curved rail sections having to be modified for each given spacing consist of a fixed frame on which a number of elements are welded to one another, they are relatively complex to machine and therefore relatively expensive; furthermore, they are bulky and, consequently, quite difficult to fit. Hence, the user of a blow-molding machine must make sufficient provision in advance when he wishes to modify the spacing of the runners, and the necessary logistics, at the expense of shutting down his machine until the new frame has been installed. Thus, it would therefore be beneficial to produce less bulky means which can be fitted more quickly and easily.
Moreover, when the containers to be transported along the runners are containers with an annular support flange, which flange surmounts a frustoconical body part, the runners must sometimes be cut to a point so as to be able to engage properly below the flange while not being blocked by said frustoconical body part situated below the flange. It would therefore be particularly advantageous to obtain sufficiently thin runners allowing engagement below any type of flange.
The Applicant has striven to solve the problems mentioned above.